http://phabricator.org is actually really great. It started in-house at Facebook. We've been using for the better part of year and I absolutely love it's code and design review tools. It also has a really nice CLI for managing your different reviews. Oh, and you don't have to worry about actually hosting the repos yourself (not worth the headache to me), you can just connect it to your github repo.

Don't be scared by the fact that it's done in PHP. It's actually really well done is very active in bringing out new updates and features.